This application relates to techniques, apparatus and systems for measuring signal properties of an optical signal, including optical polarization, polarization mode dispersion and signal-to-noise ratio.
Optical polarization is an important parameter of an optical signal in various optical systems. For example, in fiber optic communication systems, polarization-dependent effects in fibers and other devices, such as polarization-dependent loss (PDL) and polarization-mode dispersion (PMD), can have significant impacts on performance and proper operations of optical devices or systems. Hence, it may be desirable to measure and monitor the state of the polarization (SOP) and the degree of polarization (DOP) of an optical signal in these and other systems.
Optical signal-to-noise ratio (SNR) and differential group delay (DGD) of an optical signal are also important parameters for various optical devices and systems and hence monitoring of these parameters may be desirable under certain circumstances. For example, as the speed of optical wavelength division multiplexed (WDM) communication network increases to 40 Gb/s and beyond, the PMD effect of an optical transmission link need be measured and monitored to ensure transmission quality.